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California to see higher than average sea level rise, report says

June 22, 2012 | 2:48
pm

Sea levels along the California coast are expected to rise as much as 1 foot in 20 years, 2 feet by 2050 and as much as 5 1/2 feet by the end of the century, climbing slightly faster than the global average and increasing the risk of flooding and storm damage, a new study says.

That’s because much of California is slowly sinking, extending the reach of a sea that is getting hotter and expanding due to global warming, according to a report by a committee of scientists released Friday by the National Research Council.

In Washington and Oregon, where geological processes are flexing the land upward, scientists predict a less dramatic sea level rise that will be below the global average.

The report, commissioned by California, Oregon, Washington and several federal agencies, is the closest look yet at how climate change, which causes ocean water to expand and ice to melt, will raise sea levels along the West Coast.

The world’s oceans have risen about 8 inches globally over the last century and the rate is accelerating, the report notes. The world’s oceans rose about 1.7 millimeters a year in the 20th century and since 1993 the rate has increased to about 3.1 millimeters a year.

“Sea level rise isn’t a political question it’s a scientific reality,” said Gary Griggs, a coastal geologist at UC Santa Cruz and a member of the committee that issued the report.

Globally, the report predicts up to 9 inches of sea level rise in 20 years, 1 1/2 feet by 2050 and 4 1/2 feet by the end of the century.

The committee’s projections are largely in line with past estimates by scientists but substantially higher than the 2007 figures by the United Nation's Intergovernmental Panel on Climate Change because they factor in a greater contribution from melting ice.

The 274-page report was drafted by a committee of U.S. scientists that formed as a result of a 2008 executive order by Gov. Arnold Schwarzenegger, which directed state agencies to plan for the effects of sea level rise. California, Oregon, Washington and several federal agencies that sponsored the study will use it to make decisions about coping with coastal erosion and flooding that are expected to threaten homes, businesses, roads, airports and other structures that sit within a few feet of the high-tide line.

Photo: Homeowners along Broad Beach in Malibu rely on huge sandbag walls reinforced with truckloads of boulders in 2010 to stem damage. A rew report predicts faster than average water rise along the California coast. Credit: Al Seib/Los Angeles Times.